Rotary fuel pump

ABSTRACT

A ROTARY FUEL PUMP OF THE KIND IN WHICH A ROTOR HAVING A PLURALITY OF AXIALLY-EXTENDING BORES THEREIN, EACH CONTAINING A PISTON ENGAGEABLE WITH A CAM-PLATE INCLINED TO THE AXIS OF ROTATION OF THE ROTOR AND COMMUNICATING WITH A PORT AT THE END THEREOF REMOTE FROM THE CAM-PLATE, WHEREBY ON ROTATION OF THE ROTOR, THE PORTS WILL BE CARRIED IN SUCCESSION PAST A FUEL INLET AND A FUEL OUTLET APERTURE AND THE PISTONS WILL BE RECIPROCATED TO EFFECT PUMPING AND IN WHICH THERE IS A CENTRIFUGALLY OPERABLE SPILL VALVE CARRIED BY THE ROTOR AND OPERABLE TO CONTROL FLOW THROUGH A SPILL PASSAGE IN THE ROTOR LEADING FROM THE OUTLET APERTURE TO A SUMP COMMUNICATING WITH THE INLET APERTURE. IN SUCH A PUMP IT IS KNOWN TO APPLY VARIABLE CONTROLLING FORCE ON THE CENTRIFUGALLY OPERABLE SPILL VALVE. THE PRESENT INVENTION PROVIDES A PAIR OF CONCENTRIC, RELATIVELY ROTATABLE, TUBULAR QUILL SHAFTS, OF WHICH ONE IS CARRIED BY THE ROTOR AND COMMUNICATES WITH A PISTON CARRIED BY THE ROTOR AND ENGAGEABLE WITH THE SPILL VALVE AND THE OTHER EXTENDS THROUGH A WALL OF THE HOUSING OF THE PUMP TO RECEIVE AN EXTERNAL CONTROLLING PRESSURE SIGNAL. AN ANNULAR CLEARANCE SPACE BETWEEN THE CONCENTRIC QUILL SHAFTS COMMUNICATES WITH A LEAKAGE PATH FOR FLUID PROVIDING THE PRESSURE SIGNAL.

United States Patent Inventor Mark Cary Sedgwick Barnard 2,838,0296/1958 Bettoni 285/133 App No 3223: Primary Examiner-William L. FreehFiled g 22, I969 Attorney-Mawhrnney and Mawhinney Patented June 28, 1971p H Assignee gfggg Llmlted ABSTRACT: A rotary fuel pump of the kind inwhich a rotor P Se 1968 having a plurality of axially-extending borestherein, each connori y G P Baum taining a piston engageable with acam-plate inclined to the 22 5 axis of rotation of the rotor andcommunicating with a port at the end thereof remote from the cam-plate,whereby on rotation of the rotor, the ports will be carried insuccession past a ROTARY FUEL PUMP fuel inlet and a fuel outletapertureand the pistons will be 2 Chin, 1 Drawing rectprocated to effectpumping and in which there IS a centrifugally operable spill valvecarried by the rotor and opera- U.S. Cl. 417/294, bl to t ol flowthrough a spill passage in the rotor leading 417/270 from the outletaperture to a sump communicating with the Int. Cl ..F04b 49/00, Metapemlm [n such a pump it is known to apply variable 1 F04! 27/03controlling force on the centrifugally operable spill valve. The FkldDiscard! present invention provides a pair of concentric relatively 294;285/134 rotatable, tubular quill shafts, of which one is carried by theR I cued rotor and communicates with a piston carried by the rotor and e"wees I engageable with the spill valve and the other extends throughUNITED STATES PATENTS a wall of the housing of the pump to receive anexternal con- 3,085,6l9 4/1963 Penny etal. 417/294 trolling pressuresignal. An annular clearance space between 3,129,960 4/1964 Schrodt285/134 the concentric quill shafts communicates with a leakage path I1/1965 Barnard et a1. 417/270 for fluid providing the pressure signal.

SO x 532 "4t 3 3s 5s m 37 31 28 I 3o 27 26 l 9 15 3b 5 l9 5 5PATENTEUJUH281971 INvENToz MARK CARY Scmawcc EAzu/uzb ROTARY FUEL PUMPThe invention is concerned with a rotary fuel pump of the kind(hereinafter called the kind described) employed for supplying liquidfuel to a burner of a gas turbine engine and comprising a rotor having aplurality of axially-extending bores, each containing a piston urged bya spring into abutment at one end with a cam-plate inclined to the axisof rotation of the rotor, each bore communicating with a port at the endthereof remote from the cam-plate, said ports beingcireumferentially-spaced around the axis of the rotor so that, duringrotation of the rotor, the port of each bore passes successively a fuelinlet and a fuel outlet in the form of circumferentially spaced arcuateapertures, coaxial with the rotor and positioned in a stationary thrustface coacting with the endface of the rotor containing the ports of thebores.

In a known fuel pump of the kind described, the outlet aperturecommunicates with a spill passage in the rotor leading to the interiorof a housing containing the rotor and communicating with the inletaperture via a centrifugally operable valve member carried by the rotor.The known fuel pump also includes a plunger carried by the rotor andarranged to apply a variable controlling force on the valve member inopposition to the centrifugal force acting thereon. The controllingforce is applied by transmitting a fluid pressure to the plunger. In theknown pump, the fluid is oil and is applied to the rotor via apassageway defined by a circumferentially-extending seal providedbetween adjacent rotatable and stationary surfaces on the rotor and thehousing respectively. The known arrangement suffers from thedisadvantage that friction occurs at the seal. An object of theinvention is to avoid the use of such a seal.

According to the invention, a fuel pump of the kind described andincluding a centrifugally operable valve member, carried by the rotorand arranged to control flow through a spill passage in the rotorleading from the outlet aperture thereof to the interior of a housingcontaining the rotor and communicating with the inlet aperture thereof,also includes a pressure-operable device arranged to apply a controllingforce on the valve member in opposition to the centrifugal force actingthereon, means carried by the rotor defining a chamber in which thedevice is movable, and means for applying a pressure signal to thechamber, said latter means comprising a pair of concentric, relativelyrotatable, tubular quill shafts, of which one is carried by the rotorand communicates with said chamber and the other extends through a wallof said housing to means for producing said pressure signal, and apassage leading .to the outside of the housing from an annular clearancespace between the concentric quill shafts for leakage offluid providingthe pressure signal.

Conveniently, the fluid providing the pressure signal is compressed airand the passage leading from the space between the quill shafts leads toatmosphere.

Alternatively, another pressurized fluid may be employed and may bepermitted to leak through the said passage to atmosphere or to anexternal supply of said fluid.

By way of example, a liquid fuel pump in accordance with the inventionis now described with reference to the accompanying drawing which is adiagrammatic axial section through the pump.

The pump comprises a rotor I mounted in an overhung manner by means ofan integral shaft 2 in bearings 3 carried by a pump housing 4. The rotor1 includes a plurality of axiallyextending bores of which one isindicated at 50 arranged around the rotor and each including a piston 51arranged to be reciprocated as the rotor and the shaft rotate abouttheir common longitudinal axis. The ends of the piston abut throughspherically mounted shoes 52 against a stationary inclined surface 5 ofa cam-plate 6 mounted in the pump housing. The left-hand end face 7 ofthe rotor 1 contains ports, of which one is shown at 55, communicatingwith the bores 50 and spaced apart circumferentially of the rotor. Theports 55 cooperate with arcuate inlet and outlet apertures 53, 54through which, respectively, fuel contained in the interior 8 of thehousing 4.

is drawn into the axial bores 50 in the rotor and discharged to adelivery pipe (not shown), as the pistons 51 are reciprocated.

As well known in fuel pumps of this kind, the rotor 1 contains a centralspill passage 9, communicating at its left-hand end, as shown, with theoutlet aperture 54 and through radial branch pipes 10, 11 with ports 12,13 normally closed by halfball valves 14, 15 carried on leaf-springs 16,17 supported on arms 18, 19 mounted on the outside of the rotor 1. Atpredetermined rotational speeds the ports 12 or 13 will open bycentrifugal movement of the corresponding half-ball valve 14, 15 againstthe spring-loading afforded by the respective leaf spring 16, 17. Theopening of the port 12 or 13 will result in fuel being returned from theoutlet aperture 54 to the interior 8 of the housing 4 through the spillpassage 9.

Also as is well known in fuel pumps of this kind, one 14, at least, ofthe half-ball valves is engaged by a plunger 20, slidable in a chamber21 defined by the arm 18 and movable by an external fluid pressuresignal to oppose the centrifugal force acting on the half-ball valve 14.The plunger 20 carries an O- ring seal 22 to prevent leakage ofoperating fluid, applied to the chamber 21, past the plunger into theinterior 8 of the housing 4. Hitherto, the operating fluid for movingthe plunger 20 has been oil applied to the chamber 21 from outside thehousing 4 through a quill shaft or equivalent device. To prevent leakageof the oil applied to the chamber 21, it has been necessary hitherto toprovide a seal between relatively rotatable parts of the quill shaft orequivalent device, thereby leading to friction and wear at the seal.

In accordance with the present invention, a pneumatic signal is appliedto the chamber 21 from outside the housing 4. The compressed air, orother gas, providing the pneumatic signal, is applied to a connector 23mounted in an end-plate 24 secured to the housing 4. The connector 23communicates with passages 25, 26 in the end-plate 24 with a stationary,tubular first quill shaft 27, secured in a plug 28 mounted in a largediameter portion of the passage 26. The plug 28 carries O-ring seals 29;but as neither the quill shaft 27 nor the plug 28 rotates relatively tothe end-plate 24 no frictional forces atthe O-ring seals 29 occur.Surrounding the first quill shaft 27 there is a coaxial, second, tubularquill shaft 30, mounted adjacent one end thereof in a seal 31 in theend-plate 24 and adjacent the other end thereof in a bush 32 insertedinto a central socket 33 in the right-hand end face of the rotor 1. Thesecond quill shaft 30 carries an O-ring seal 34 engaging the bush 32;but as the latter rotates with the rotor 1 and is not rotatablerelatively thereto, no frictional forces occur at the O-ring seal 34.The quill shaft 30 runs freely on the quill shaft 27, there being anannular running clearance space therebetween. The socket 33 is formedcoaxially of the spill passage 9 but flow is prevented therebetween by aball 35 plugging a portion 36 between the passage 9 and the socket 33. Abranch duct 37 leading to a socket 38 communicates with the passageportion 36 between the ball 35 and the socket 33. The socket 38 has atubular connector 39 therein leading to a socket 40 in a portion of thearm 18 adjacent the chamber 21 defined therein. The connector 39 issealed at its ends by O-ring seals 41, 42 and communicates with apassageway 43 in the arm 18 leading from the socket 40 to the chamber21. The passageway 43 is closed to the interior 8 of the housing 4 by aball plug 44.

The end of the running clearance space between quill shafts 27 and 30 atthe right-hand end, as shown, of the quill shaft 30 communicates with acavity 45 in the end-plate 24 and closed by the seal 31. The cavity 45communicates through a passageway 46 with the outside of the end-plate24.

When a pneumatic signal is applied through the connector 23, it will betransmitted through the passage 25, the quill shaft 27, the quill shaft30, the duct 37, the connector 39 and the passageway 43 to the chamber21. The only place where leakage of compressed air can occur is throughthe annular running clearance space between the quill shafts 27 and 30to the cavity 45. From the cavity 45, the leakage compressed air willflow to the outside of the end-plate 24. The leakage is small and isreadily replenished without affecting the controlling signal applied tothe chamber 21. The seal 31 prevents leakage of compressed air from thecavity 45 into the fuel in the interior 8 of the pump housing.

The only seal acting between rotating and stationary parts in the quillshaft arrangement provided by the present invention is the seal 31; butas this acts between pump inlet pressure and atmospheric pressure, thepressure differential across it is extremely small and therefore therewill be substantially no wear at the outer cylindrical surface of thequill shaft 30. The clearance between the quill shafts 27 and 30 avoidswear of the inner cylindrical surface of the quill shaft 30 and theouter cylindrical surface of the quill shaft 27.

Instead of applying compressed air to the plunger 20, via the quillshafts 27 and 30, another pressurized fluid may be applied from a supplyexternally of the housing and in that case the cavity 45 may communicatewith the external supply instead of with atmosphere, so that the leakagefluid will be returned to the supply What I claim as my invention anddesire to secure by Letters Patent of the United States is:

Iclaim:

L A rotary fuel pump comprising a housing, a rotor mounted in saidhousing and having a plurality of axially-extending bores therein, apiston in each said bore, a cam-plate inclined to the axis of rotationof the rotor, a spring in each said bore urging the piston therein intoabutment with said cam-plate, each said bore communicating with a portat the end thereof remote from the cam-plate, said ports beingcircumferentially spaced around the axis of the rotor and cooperablesuccessively with a fuel inlet and a fuel outlet in the form ofcircumferentially-spaced arcuate apertures coaxial with the rotor, acentrifugally operable valve member, carried by the rotor and arrangedto control flow through a spill passage in the rotor leading from'theoutlet aperture to the interior of said housing and communicating withthe inlet aperture, a pressure-operable device for applying acontrolling force on the valve member in opposition to the centrifugalforce acting thereon, means carried by the rotor defining a chamber inwhich the device is movable, and means for applying a pressure signal tosaid chamber, wherein the improve ment comprises said latter meansincludes a pair of concentric, relatively rotatable tubular quillshafts, of which one is carried by said rotor and communicates with saidchamber and the other extends through a wall of said housing to meansfor producing said pressure signal, there being an annular clearancespace between the concentric quill shafts communicating with a cavityformed in a wall of the housing to receive any fluid providing saidpressure signal that may have leaked through said annular clearancespace, and an annular seal engaging between said quill shaft carried bythe rotor and a peripheral wall of said cavity.

2. A fuel pump as claimed in claim 1 in which the fluid providing thepressure signal is compressed air and a passage leads from said cavityto the outside of said housing to lead leakage compressed air from saidcavity to atmosphere.

